Concrete is a durable material that is widely used in the construction industry. Although it is often poured into moulds on site, concrete castings tend to be preferred for specialist jobs. Manufactured off-site, castings are assembled together after transportation to the place they need to be. Protecting highly-engineered concrete castings is, therefore, imperative to prevent damage during the transportation stage. In addition, the correct protective coatings will allow for a casting to function well in situ. Even a tough material like concrete can be susceptible to wear and tear unless steps are taken to protect it, but how is this done?
Thin Film Coatings
Concrete may be able to withstand impacts and abrasion, but it can also crumble if it is knocked into at any weak points. Reinforced concrete compresses it so that it is more impact-resistant, but this does not help if it is chipped away at by people or machinery rubbing into it repeatedly. Therefore, a thin film coating is often applied to concrete castings which may suffer this fate. For example, a casting that acts as a set of steps or to form a paved area may require a thin layer of protection over the top to prevent the concrete from wearing down. Acting rather like a layer of varnish on woodwork, concrete thin film coatings create a seal that is little more than a millimetre in thickness.
Water-based acrylic coatings are popular. These dry rapidly and have a clear appearance so don't interfere with the look of the casting, especially if it to be used alongside uncoated concrete. However, they have lower performance ratings than solvent-based acrylics and tend not to last as long. Although more protective, some solvent-based acrylics will discolour in sunlight or produce an unwanted aroma.
Thick Film Coatings
These coatings are more noticeable when applied to concrete if viewed close up. They are generally two to three millimetres thick, but some products of this type require much thicker applications. Most contain two-part, epoxy and polyurethane ingredients which are combined with a hardener that helps them to become dense quickly when sprayed on. Unfortunately, polyurethane is not always good at sticking to concrete, depending on the type of casting, so polyaspartic coatings are also used. These cure rapidly and provide an even layer of protection as well as providing a good degree of UV-resistance. Even in places of high humidity, this type of coating can prevent unwanted film bubbling, too. However, it tends to be a more expensive option.